From 87b6559d0a37cd82b4b2ffe38f88c0d4ac6ee7e2 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Mon, 25 May 2015 11:27:46 +0200 Subject: [PATCH] x86/fpu: Improve xstate_fault() handling There are two problems with xstate_fault handling: - The xstate_fault() macro takes an argument, but that's propagated into the assembly named label as well. This is technically correct currently but might result in failures if anytime a more complex argument is used. So use a separate '_err' name instead for the label. - All the xstate_fault() using functions have an error variable named 'err', which is an output variable to the asm() they are using. The problem is, it's not always set by the asm(), in which case the compiler might optimize out its initialization, so that the C variable 'err' might become corrupted after the asm() - confusing anyone who tries to take advantage of this variable after the asm(). Mark it an input variable as well. This is a latent bug currently, but an upcoming debug patch will make use of 'err'. Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/x86/include/asm/fpu/internal.h | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index d142ecb067b8..5370500d479e 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -220,13 +220,13 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu) \ ".section .fixup,\"ax\"\n" \ \ - "3: movl $-1,%[err]\n" \ + "3: movl $-2,%[_err]\n" \ " jmp 2b\n" \ \ ".previous\n" \ \ _ASM_EXTABLE(1b, 3b) \ - : [err] "=r" (__err) + : [_err] "=r" (__err) /* * This function is called only during boot time when x86 caps are not set @@ -245,14 +245,14 @@ static inline int copy_xregs_to_kernel_booting(struct xregs_state *xstate) asm volatile("1:"XSAVES"\n\t" "2:\n\t" xstate_fault(err) - : "D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask) - : "memory"); + : "D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask), "0" (err) + : "memory"); else asm volatile("1:"XSAVE"\n\t" "2:\n\t" xstate_fault(err) - : "D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask) - : "memory"); + : "D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask), "0" (err) + : "memory"); return err; } @@ -272,14 +272,14 @@ static inline int copy_kernel_to_xregs_booting(struct xregs_state *xstate, u64 m asm volatile("1:"XRSTORS"\n\t" "2:\n\t" xstate_fault(err) - : "D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask) - : "memory"); + : "D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask), "0" (err) + : "memory"); else asm volatile("1:"XRSTOR"\n\t" "2:\n\t" xstate_fault(err) - : "D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask) - : "memory"); + : "D" (xstate), "m" (*xstate), "a" (lmask), "d" (hmask), "0" (err) + : "memory"); return err; } -- 2.20.1